Steel pilings are usually filled with grout/concrete and rebar. Pilings are not designed to rely on the wall strength alone for their ability to carry a load.

In addition, these are most likely friction piles, where they will be driven to refusal, but not necessarily to bedrock. The fluting will give greater surface area to the pile to aid in increasing the friction with the surrounding soil.

No graffiti on the boxcars. Makes for a delightful view.

Washington DC was altered so radically by urban renewal during the 21st Century that guessing the locations of some Shorpy photographs can be a real challenge. I propose Maine Avenue at 14th Street SW, looking eastward:

I'm conjecturing that fluting the walls like that allowed them to be thinner, an important consideration in 1942. But I wonder how well they'd hold up against rust.

Those are the biggest candles I've ever seen.